Direct modulation transmitter utilizing signals squaring

Abstract

A apparatus to provide a direct modulation transmitter having high dynamic range and low distortion using signal processing at a first frequency level for a signal to be transmitted and increasing frequency to transmission frequency in a manner to avoid distortion and utilizing a squaring function in up-converting basic processing signal.

1. A direct conversion transmitter comprising:
 signal means providing an input signal at a baseband frequency;
 a square root circuit receiving the input signal and providing a modulation input signal for a modulator at a square root of the input signal at the baseband frequency; 
 the modulator modulating the output of the square root circuit, the modulator operating on a modulation frequency of one half RF, where RF is a transmission frequency of the direct conversion transmitter, to convert the input signal to one half RF; 
 a variable gain amplifier coupled to the output of the modulator, 
 a squaring circuit coupled to an output of the variable gain amplifier and squaring the modulated signal to convert the output of the variable gain amplifier to the transmission frequency; and 
 gain control means for providing dynamic range in the transmission frequency, the gain control means providing an output for coupling to a transmission antenna. 
 
 
   
   
     2. The transmitter according to  claim 1  wherein the signal means provides an in-phase signal and quadrature signal for modulation and wherein the modulator comprises a Gilbert cell modulator. 
   
   
     3. The transmitter of  claim 2  wherein the circuit is comprised in a digital signal processor receiving the input signals. 
   
   
     4. The transmitter of  claim 2  wherein the square root circuit comprises an analog circuit. 
   
   
     5. The transmitter of  claim 3  wherein the squaring circuit comprises a Gilbert multiplier. 
   
   
     6. A direct conversion transmitter comprising:
 signal means providing an input signal at a baseband frequency;
 a square root circuit receiving the input signal and providing a modulation input signal for a modulator at a square root of the input signal at the baseband frequency; 
 the modulator modulating the output of the square root circuit, the modulator operating on a modulation frequency of one half RF, where RF is a transmission frequency of the direct conversion transmitter, to convert the input signal to one half RF; 
 a squaring circuit coupled to an output of the modulator and squaring the modulated signal to convert the output of the modulator to the transmit frequency; and 
 gain control means for providing dynamic range in the transmission frequency, the gain control means providing an output for coupling to a transmission antenna. 
 
 
   
   
     7. The transmitter according to  claim 6  wherein the signal means provides an in-phase signal and quadrature signal for modulation and wherein the modulator comprises a Gilbert cell modulator. 
   
   
     8. The transmitter of  claim 7  wherein the square root circuit is comprised in a digital signal processor receiving the input signals. 
   
   
     9. The transmitter of  claim 8  wherein the squaring circuit comprises a Gilbert multiplier. 
   
   
     10. The transmitter of  claim 7  wherein the square root circuit comprises an analog circuit.